1. Field of the Invention
The present invention relates to gimbal support assemblies, and more particularly to a flexure mounted gimbal support assembly which provides a low rotational stiffness over limited angles.
2. Description of Prior Art
To improve guidance accuracy inertial measurement units use inertial components which are more sensitive to environmental inputs. To isolate these components from undesirable environmental inputs, maximum base-motion isolation is desired. Traditionally, inertial components are hard mounted on a "stable" platform which can be independently positioned rotationally through the use of gimbals (see FIG. 1). External system vibrations, such as shock pulses, are dampened through shock mounts which reduce translational motion within the system to acceptable limits.
To further improve the stability of the stable platform, base-motion isolation in the rotational sense is needed. A conventional gimbal support bearing assembly is shown in FIG. 2 and has:
a stub shaft to provide structural attachment to the stable platform; PA1 a ball bearing to provide rotational support between gimbals; PA1 a slip-ring assembly to provide electrical power and signal information to and from the inertial components; PA1 a torque motor to provide driving torque to rotate the gimbals; and PA1 a bearing housing to provide structural attachment to the gimbal. PA1 require an external power supply; PA1 have potential leakage problems; PA1 require rotary seal joints; PA1 impose a weight penalty on operational hardware; and PA1 increase cost.
The stick-friction behavior of the gimbal support bearings, slip-rings, torque motor brush friction and torque motor magnetic drag are major factors that limit the degree of base-motion isolation. Traditional concepts of eliminating or minimizing bearing friction, such as gas or a liquid fluid, have had the following disadvantages:
Another concept, the dual co-axial bearing which provides low friction when the intermediate race is oscillated or rotated, also has the disadvantage of requiring an external power supply to drive the intermediate bearing race. Neither of these concepts solve either the slip-ring or the torque motor friction problems.
Therefore, a device that eliminates or minimizes the stick-friction effects on rotary components without requiring external power sources is desired.